Preparing dye paste for printing and dyeing



March 14, 1933. R O. WOQD ,9l,275

PREPARNC- DYE PASTE FOR PRINTING AND DYEING Filed Aug. 25, 1929 rammed Mar. 14, 193e UNITED 'STATES inerzia PATENT ortica ROBERT O. WOOD, OIE' HAMBURG, NEW YORK, ASSIGNOR TO NATIONAL ANILINE &

CHEMICAL COMPANY, INC., OF NEW "YORK, N..Y., A CORPORATION OF NEW. YORK PREPARING DYE PASTE FOB PRINTING AND DYEING Application led August 26, 1329. Serial No. 388,526.

This invention relates to the production of smooth dye pastes, free from lumps and grit or other foreign matter, to be used for printing and dyeing. y

In the printing of designs on fabrics, the dye is applied b means of a copper roll, in the surface of w ich is engraved the design to be printed on the cloth. This roll is smooth and polished,'except where the depressions o the engraving occur.

`ln operation, the surface of the roll is completely coated with the dye paste mixed with a thickening agent and other wellknown ingredients, so .that the smooth portions of the roll as well as the engraved portions are coated. The paste is then scraped cleanly from the smooth portions with a scraping device called a doctor, leaving the depressions in the roll filled with dye paste.

In printing, the cloth is pressed against the prepared roll which rotates at the same speed and in the same direction as the cloth travels. Since the smooth portions o the roll are free from dye paste, these portions will impart no paste to the cloth, but the cloth will pick up the paste retained in the depressions and crevices of the engraved design. The design of the roll will thereby be continuously transferred to the cloth.

The dye pastes offered to -the trade for use in printing are dispersions of finely divided particles of insolubledyestuii in water and, in general, have a consistency ranging, for'example, from thatof glycerine to that of molasses.. @It is necessary that these pastes, which are used for printing in the above described manner, shall be absolutely free from lumps and grit. Especially is this true of vatdyestui pastes. Since the rolls are made of soft copper, any grit present in the dye paste is liable to score the smooth portions of the roll whenscraped oif by the doctor. Any depression in the roll= such as a scratch,even though hairlike, will become lled with the dye paste -when the roll is coated. When the paste is scraped oifA the roll to prepare it for the printing operation, a bit of dye paste `will remain in such a. depreion. In printing,

this hit of dye paste .be transposed to the cloth, imparting thereto a blemish in the printed design.

A scratched or scored roll can be repaired only by resurfacing the roll, re-engraving the design thereon and repolishing the surface. Such a procedure is expensive.

Since the striations of the engraving are' generally line, it is necessary that the particles of dye which constitute the paste shall be small and uniformly dispersed. Such a paste will fill uniformly the striations of the design in the roll and will be imparted as an even coating to the cloth in the printing opera-tion. Lumps even "as small as a pinhead are objectionable. Any large lumps present in the dye paste may be scraped out of the striations of the design, leaving an uncovered space which will be imparted t0 the cloth as a blank. Smaller lumps of dye which are not uniformly distributed throughout the paste may not be scraped oit' by the doctor and consequently will produce a heavier/spot on .the inished print, resulting in uneven dyeing. In dyeing by the pad and jig method (pigment padding method), it is equally important that the paste be free from lumps, otherwise dyeings made with such a paste will show little dark spots i and streaks,t due to the heavier dyeing effect of the lumps. l p

Heretofore, it .has been proposed to eliminate lumps and 4grit Jfrom such pastes, by

subjecting them to grinding in a paint mill.

In this way, the grit has been disintegrated into particles too fine to scratch the rolls,

and lumps of dye paste have been broken up.

But the operation of grinding requires large power consumption,.and is exceedingly slow. With a small outlay for equipment, output is greatly retarded. A large outlay for apparatus is necessary to speed up the capacity of the grinding operation.

Attempts have also been made 'to screen, n

the pastes, by passing them through a vibratory or gyratory screen, of about 200 mesh. However, the pastes are so thick that they will not low through the screen when it is at rest and will scarcely flow through when brushed across its surface. While some will pass through the -screen in motion, this been foundthat the screening operation is also slow. Also, because of the strain on the cloth, even the strongest screens soon break. A break in the screen necessitates the resereening of the Whole batch, since grit and lumps must be absolutel eliminated.

Accor ing to the present invention, it has rit can be eliminated and lumps can be bro ien up by directing a stream of the dye paste against a foraminousV member, such as a fine screen, preferably at,

an acutel angle to the surface of the member. This method is to be distinguished from atomizing methods wherein a thin stream of material is sprayed under high velocity algainst a screen, for the purpose of breaking t e material up into a mist. In the present instance, the stream need not necessarily be tine and need not necessarily move under high velocity.

This method is also to be distinguished from the processes wherein material is foi-ced against a screen under a static pressure head. When dye pastes of this type are forced against a. screen under a static pressure head, the solid particles act as a filter bed and prevent the paste from passing through. To

prevent the screen acting as a filter, itis therefore important that the air pressures on b oth sides of the screen be substantially equal. One Way in which this is ensured is by having the area of the screen greater than the cross section area of the stream of dye paste, and having both sides of the screen exposed to the free atmosphere;

The nature of the invention having been indicated above, it will be apparent that one object thereof is to provide a method :of preparing dyestufs in the form of smooth pastes free from grit or large particles. 4 Another object is to provide dye pastes wllich shall print evenly from a printing ro y A further object is to provide dye pastes which do not scratch the soft copper rolls used in printingl cloth with dyes.

A simple form of apparatus suitable for carrying out the process of the present in#` vention, which apparatus ismore fully described in the United States Patent N o. 1,810,935 of Robert O. Wood and Byron L. West, June 23, 1931, is shown in the accompanying drawing, wherein the figure is a diagrammatic representation of one form of the apparatus. Referring to the drawing, a cylindrical section of pipe 1 of large diameter is closed at one end by a head 2, except for certain openings to be later described. Within pipe l is located a fine metallic screen 3 of, say, 200 mesh. The head 2 is bored and threaded at 4 to receive the vertical pipe 5 through which the material to be screened is introduced. At about right angles to this aperture 4, the head is tapped alud threaded at 6 to receive the horizontal outlet pipe 7, through which the unscreened 'material is discharged. 'Intermediate between these apertures, the head is alsotapped as at 8,' to 'provides a vent. In operation, a pipe is inserted in this vent to prevent material from splashing out. Screen 3, above a container (not shown) to a' point close to the face of the screen. Velocity is imparted to this paste by subjecting the interior of the container to pressure, or by having the surface of the paste in the container at a higher level than the end of the pipe. In this apparatus, 'the paste is directed against the screen under a velocity head in excess of that of normal gravity flow o f said paste across Said screen. The stream of paste sweeps across the screen and fine material and disintegrated lumps pass through the screen and are collected. Coarse material, such as grit and lumps larger than the apertures ofthe screen, do. not pass through but are carried or swept olf the surface on the approach side. This coarse material, or run-olf, may be collected vand recirculated until all the dye lumps have been broken up and have passed through the screen. A residue of grit and foreign matter remaining can be discarded. The pi e 7 serves to carry away the stream of ye paste to be returned t o the container forl repassage across the screen. The opening 8 insures that the air pressures on both sides of the screen willl be substantially equal so that there will be no tendency for thescreen to act as a filter. The sweeping and dynamic action of the stream'onto and across the-face of the Screen contributes to break up the lumps present in the d-ye, paste and force the liquid and finely suspended particles through the screen. A colloid mill may be used in connectio with the screening process to homogenize the paste, but it is to be understood that the colloid mill alone does not disintegrate all the grit. The process can be used in the manufacture of pastes of Indanthrene yeli which passes through the interstices will be governed the screened dye intended to cover the screening of dye pastes of all consistencies through screens of all sizes. rl`he invention is limited to the screening of dye pastes, so thick-through screens so fine, that under the static influence of gravity but little material will pass through a horizontal screen. The invention, as defined in the following claims, accordingly is to be construed as limited with regard to the size of the interstices of the screen, and the consistency of the dye paste.

I claim: y

1. In the process for screening a dye paste which is so viscous through a screen which is so fine that under the static iniuence of gravity little of the paste will pass therethrough, the improvement which comprises sweeping a body of said dye paste across and in contact with the surface of the screen under the influence of an initial velocity head in excess of that due to normal gravity iow directed at an acute angle to the surface of the screen, and collectin the dye paste of the by the use to he made of screen.

2..,'Ihe process of screening an aqueous suspension comprising a water-insoluble organic dyestuif in finely divided condition and larger particles of foreign material, which comprises forcibly projecting a stream of said suspension at a velocity in excess of thatYV of normal gravity flow against a foraminous member the openings of which are so fine that under the static iniiuence of gravit little of the suspension will pass theret rough, and collecting the suspension which passes through said member.

3. The process of screening an aqueous suspension comprising a water-insoluble organic dyestui in finely divided condition and larger particles 4of foreign material, which comprises forcibly projecting astream of said suspension, at a velocity in excess of that of normal gravity iiow against a foraminous member the openings of which are so ine that under the static iniuence of gravity little of the suspension will pass therethrough, an acute angle to the surface of said foraminous member and impinging upon an extended eifective area of said member, and collecting the suspension which passes through said member. A

4. The process of screening a dyestuif paste containing grit and comprising an/ l aqueous suspension of a Water-insoluble organic dyestui in finely divided condition, which comprises forcibly projecting a stream of said paste, at a velocity in excess of that of normal gravity How, against a foraminous member the openings -of which arev that under the staticV iniiuence of gravity little of the pastev will pam therethrough,

paste. However, it is notv aqueous suspension of a vat dyestuff in said stream being directed atso .A fine A said stream being of smaller cross-sectional area than the area of said member and impinging upon an extended effective area. of said member, equalizing the pressure upon both sides of said effective area, andcollecting the paste which passes through said member.

5. The process of screening a dyestuif paste containing grit and comprising an nely divided condition, which comprises forcibly projecting a stream of said said paste, at a velocity in excess ofv that of normal gravity iow, against a screen the openings of which are so fine that under the static inuence of gravity little of the paste will pass therethrough, said stream vbeing directed at an acute angle to the surface of said screen and impinging upon an extended effective area of said screen, equalizing the pressure upon both sides of said screen, and collecting the paste which passes through said screen.

6. The process of screening -a dyestuf paste `containing grit and comprisin an aqueous suspension of a vat dyestuii:l in nely divided condition, which comprises forcibly projecting a stream of said paste, at a velocity in excess of that of normal gravity flow, against a screen the openings of which arefso fine that under the static inuence of gravity little of the pastewvill pass therethrough, collecting the .paste which passes through said screen, and withdrawing and returning for re-screening the paste not passing through said screen.

aoV

7 The process of screening a d yestuif 'v paste containing grit and comprising all y aqueous suspension of a vat dyestuif in finely directed at an acute angle-to thesurface of said screen and impinging upon an extended effective area of said screen, equalizing the pressure upon both sides of said screen, an collecting the paste passing through the effective area.

In testimony whereof I aix mysignature. f ROBERT O.,- WOOD.

n CERTIFICATE oFcoRREcT'IoN.

Pawn No. 1,901, 275./ v lMarch 14, 1933.

` AROBERT o. Woon.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 3, line 77, claim 5, strike out "said" second occurrence; fine 115, claim 7, for "screen" read "effective area", and lines 116 and 117, for ."effective area" read "screen"; and that the said Letters Patent should be read with these corrections therein that the saine mayY conform to the record of the-case in the Patent Office.

Signed and sealed this 16th day of May, A. D. 1933.

' no Je (Seal) Acting Commissioner of Patents; 

